Simple differential amplifiers with relatively straightforward output active loads are typically configured with two N-channel devices having the source/drains thereof connected between respective differential outputs and ground. The gates of the two N-channel transistors are connected to a separate bias voltage, which bias voltage can be generated at any desired voltage with a separate circuit. For a single ended output voltage, a simple differential amplifier with an active load provides the bias voltage by connecting the drain and gate of one of the N-channel transistors together, the drain of the other N-channel transistor providing the single ended output. In this manner, the current in the transistor having the drain and gate connected together is mirrored over to the other N-channel transistor, the gates being common. In order for their to be proper operation of this active load, the currents in the two N-channel transistors must mirror each other and the drain impedance of the one transistor having the drain and gate connected together must be low, and the drain impedance on the output must be high. For the simple active load, an N-channel transistor having the gate and drain tied together in a diode-connected configuration is by definition operating in the saturated region and, therefore, the current mirror formed by the two N-channel transistors will work properly.
In a ratioed cascoded load, an additional N-channel transistor is disposed in series with the drain of the diode-connected N-channel transistor such that the diode connection occurs between the drain of the additional N-channel transistor and the gate of the original N-channel transistor. A similar configuration is incorporated in the output leg wherein an additional N-channel transistor is incorporated in series with the drain of the original N-channel transistor in the output leg. Both of the additional transistors have the gates thereof connected to a bias voltage. With careful choice of the device sizes in this type of configuration, the two transistors in the diode-configured side of the mirror can be operated in the saturated region. However, when utilizing a triple cascoded configuration, this method has difficulties. In this configuration, a level shift circuit is typically utilized. However, this level shift circuit can cause problems, such as additional power draw, overall output voltage swing, and stability problems.